1. Field of the Invention
The present invention relates to a method for setting a working condition in off-line teaching to be preferably used to set, for example, a welding condition for a robot equipped with a welding gun.
2. Description of the Related Art
Recently, in order to apply a robot to a variety of workings, in general, a variety of tools are attached to a face plate of a robot arm to allow the robot to perform the workings.
In the meantime, there have been hitherto suggested a large number of teaching techniques directed to the robot as well as a large number of techniques for variously correcting teaching data used for such teaching techniques. For example, those suggested in relation to the teaching technique for the robot include a method in which information necessary for an employed robot working is dealt with in order to respond to the request of the user as accurately as possible while mitigating the load exerted on the user as less as possible (see Japanese Laid-Open Patent Publication No. 5-27828).
Those suggested in relation to the technique for correcting teaching data include, for example, a method in which it is possible to easily execute revision for the teaching point and correction for the teaching locus under the same operating condition as that used during playback even at a place separated from the working site so that the load on the operator is mitigated to perform the operation for revising the teaching (see Japanese Laid-Open Patent Publication No. 8-286726), a method in which any positional deviation can be corrected highly accurately and automatically for all positions of striking points (see Japanese Laid-Open Patent Publication No. 7-325611), a method in which the position of a robot is corrected by using a neural network (see Japanese Laid-Open Patent Publication No. 6-114769), a method in which a correcting operation sensually comprehensible for the operator can be performed when conversion data concerning the robot action is revised if any abnormal situation concerning the action range occurs in revised teaching data (see Japanese Laid-Open Patent Publication No. 5-289730), a method in which a repeated logical operation based on the modified Powel method is applied to respective factors of unknown variable matrix and constant matrix so that the accuracy is further improved and the operation speed is further increased in order to avoid any measurement on the rectangular coordinates and ensure the absolute positional accuracy of an arm-type articulated robot only by using the angle of rotation about the arm axis (see Japanese Laid-Open Patent Publication No. 6-274213), and a method in which correction is automatically made for any preset error concerning the constant and any preset error concerning the tool offset which are preset data for an articulated robot having a tool attached to a wrist of the robot (see Japanese Patent No. 2520324).
Those suggested in relation to the technique for setting the tool tip point include a method in which the tool tip point can be set in a desired posture in accordance with a simple procedure by using a simple setting jig even when no design data is available (see Japanese Laid-Open Patent Publication No. 7-191738). Those suggested for using CAD data include a method in which it is unnecessary for the operator to input initial preset data, working route data, and working action data one by one so that the amount of input performed by the operator is greatly decreased (see Japanese Laid-Open Patent Publication No. 8-286722). Those suggested in relation to the locus display include a method in which the relative positional relationship between a workpiece and a position of an acting actual tool can be recognized easily and accurately when the workpiece is retracted from a working position (see Japanese Laid-Open Patent Publication No. 8-174454).
When the off-line teaching technique as described above is applied to a robot equipped with a welding gun, it is indispensable to set the welding condition in addition to the teaching made for the tool tip. The welding condition includes, for example, the change (sequence) of the welding current in accordance with the passage of time, the peak value of the welding current, and the welding time.
However, in the case of the conventional off-line teaching technique, it is impossible to easily obtain information, for example, on the material quality and the plate thickness of the workpiece to be welded, during the process of the off-line teaching. Therefore, a problem arises in that it takes an extremely long time to decide all of the welding conditions for the workpiece.
For this reason, in the conventional technique, the operator temporarily sets an appropriate welding condition in view of the shape and the thickness of the workpiece. In such a procedure, when the off-line teaching data is downloaded to an actual robot, it is necessary to perform an operation for resetting the temporarily set welding condition in conformity with the actual robot, i.e., it is necessary to perform an operation for setting the welding condition again. Therefore, a problem arises in that such a process contrarily takes a long time.
Recently, a method is available, in which working conditions and attributes of the workpiece data are provided for respective elements to add a function to assist the off-line teaching operation. However, in this method, the working condition is decided by the operator by means of selection from those displayed on the monitor. Therefore, every time when the working condition is registered, it is necessary for the operator to select an optimum condition from several working conditions indicated in a table. As a result, a problem arises in that the operation is complicated. Further, this method greatly depends on the skill of the operator. Therefore, there has been a fear that it is difficult to set the optimum condition.